1. Field of the Invention
The invention relates to a device for dynamic-mechanical analysis of samples, wherein on a rigid support with uprightly aligned longitudinal axis along a linear force transmission path extending parallel thereto the following are arranged: an electromechanical transducer, connected to the force transmission path, for introducing a mechanical force corresponding to an electrical drive signal; a sample holder with two holding parts which are deflectable relative to one another along the force transmission path, wherein the force introduced by the transducer is coupled to one of them and a first area of the sample can be fastened thereto, and wherein the reaction force opposite to the introduced force is supported on the other one and a second area of the sample, spaced from the first area, can be fastened thereto; a device for measuring the deflection, caused by the introduced force, of the two holding parts relative to one another; and an adjusting device with a connector part connected to one end of the force transmission path which is adjustable transverse to the longitudinal axis along a first spatial axis and along a second spatial axis perpendicularly arranged to the first spatial axis.
2. Description of the Related Art
With such devices material properties of samples, for example, their modulus of elasticity, are examined by periodic force action on the sample. In this connection, it is desirable to perform the test with high precision across a broad frequency range. In this respect, however, there is the problem of undesirable vibrations, in particular, in the range of high frequencies. Moreover, for achieving a good measuring precision, a precise adjustment relative to the linear force transmission path is required.
It is an object of the present invention to improve a device of the aforementioned kind with respect to the measuring precision and the usable frequency range.
In accordance with the present invention, this is achieved in that the adjusting device comprises a first carriage which is slidably guided along the first spatial axis as well as a pivot frame, which is slidably guided on the first carriage on a first cylindrical guiding surface segment with a first cylinder axis which is parallel to the first spatial axis, and a second carriage, which is slidably guided on the pivot frame along the second spatial axis, on which second carriage the connector part is guided on a second cylindrical guiding surface segment with a second cylinder axis which is parallel to the second spatial axis.
With the inventive embodiment of the adjusting device, not only the point of attack of the introduced force on the sample holder can be adjusted in a plane which extends perpendicularly to the longitudinal axis, but also the direction of the introduced force. In this connection, the connector part is subjected to such a guiding action by the two cylindrical guiding surface segments that it is focused in its longitudinal direction on the two cylinder axes. The adjustability of the spatial angle achievable in this way and the transverse adjustments taking place along the two spatial axes are independently adjustable relative to one another within the frame of the required adjusting range and precision. A further advantage of the adjusting device embodied according to the invention resides in its compact configuration and minimal space requirement.
Expediently, it is suggested that the first and the second cylinder axes intercept one another. Such a selection of the curvature radii and spatial arrangement of the two guiding surface segments favor the degree of independence of the transverse adjustment and spatial angle adjustment. This contributes significantly to an increase of the operating convenience.
According to an expedient embodiment, it is suggested that, for adjusting in the direction of the first spatial axis, the first carriage is guided in a stationary frame-shaped lower housing part in which a first threaded spindle is rotatably supported which extends axially in the first spatial direction and engages a thread of the first carriage. In this connection, the degree of adjustment in the first spatial direction is determined by the pitch of the first threaded spindle and the respective magnitude of its rotation.
Another expedient embodiment is characterized in that the first cylindrical guiding surface segment is formed by two circular disc segments provided on two end faces, extending transversely to the first spatial axis, of the first carriage, between which the pivot frame is arranged and supported on recesses with a complementary configuration provided on its corresponding end faces. In this way, the construction height in the longitudinal axis is kept particularly small.
With respect to the adjustability in the second spatial direction, the device can be expediently configured such that the second carriage is guided in that pivot frame in which a second threaded spindle is rotatably supported and extends axially in the second spatial direction and engages a thread of the second carriage. In this connection, the pitch of the second threaded spindle and the respective rotation imparted thereon determine the adjustment in the second spatial direction.
Moreover, it is expedient, in particular, with respect to a minimal construction height, to design the device such that the second cylindrical guiding surface segment is formed by two cylindrical mantle segments formed on two end faces, extending transverse to the second spatial direction, of the second carriage on which cylindrical mantle segments the connector part is supported by means of gliding surfaces complementarily embodied thereto.
For the total configuration of the device it is also advantageous that the connector part has a projection extending in the longitudinal direction and penetrating through cutouts of the carriage and the pivot frame. In this way, the connector part with its projection is freely accessible via an end face of the adjusting device so that the connection of force transmission members acting along the force transmission path is facilitated.
For adjusting the spatial angle in a plane perpendicular to the first spatial axis, the device is expediently configured such that in a stationary upper housing part a third threaded spindle is rotatably supported which extends axially in the second spatial direction. A driver engaging the pivot frame is guided on its thread. The pitch and rotation of the third threaded spindle determines the displacement of the driver along the second spatial direction and thus the position of the pivot frame, entrained by the driver, on the first cylindrical guiding surface segment. This determines the angular adjustment in planes perpendicular to the first spatial axis.
For adjusting the spatial angle in planes perpendicular to the second spatial axis, the device is expediently designed such that in a stationary upper housing part a fourth threaded spindle, which extends in the axial direction in the first spatial direction, is rotatably and axially slidably supported. It is coupled by a first driver with the second carriage, and a second driver is guided on its thread and engages the connector part. As a result of this coupling with the second carriage, the fourth threaded spindle follows the adjusting movement along the first spatial axis while, as a result of its rotation, the second driver is correspondingly moved according to its pitch along the first spatial axis, and the connector part coupled with the second driver is thereby moved correspondingly on the second cylindrical guiding surface segment so that the spatial angle is adjusted in the planes parallel to the second spatial axis.
Within the context of the invention it is furthermore provided that on the parts, guided on the threads of the threaded spindles, indicator pins are secured which extend parallel to the threaded spindles. Since the transverse adjustment of the connector parts along the first and second spatial axes is determined by the position of the first and second carriages on the threads of the first and second threaded spindles and the spatial angle adjustment by the position of the drivers on the threads of the third and fourth threaded spindles, the indicator pins secured on these parts show the operator relative to the corresponding threaded spindles the adjustments of the transverse position and of the spatial angles.
Another contribution to the solution of the object is achieved, in particular, for a device of the aforementioned kind in that the sample holder has a housing with a receiving chamber, extending through the housing longitudinally to a transverse axis which is oriented transverse to the longitudinal axis, for a three-part insert whose central part, when viewed in the direction of the transverse axis, forms the first holder part and is positive-lockingly supported in a ring, which is arranged with play in the receiving chamber, and whose lateral parts on both sides of the central part form the second holder part and are supported positive-lockingly in the receiving chamber. Also provided are an opening for penetration by a force transmission member extending on the longitudinal axis and connected to the ring and a connecting area positioned opposite the opening, when viewed in the direction of the longitudinal axis, for a member serving to receive the reaction force.
This configuration of the sample holder is, on the one hand, advantageous with respect to the oscillation behavior and the stability requirements. On the other hand, it provides the ability for receiving differently designed samples and is easy to handle. In particular, these advantages are achieved when the central part and the two lateral parts are formed as cylindrical discs with circular end faces extending radially relative to the transverse axis. This configuration is suitable, in particular, for examining samples under shearing load. In this connection, the samples are clamped between the circular end faces of the central part and of the two lateral parts.
An embodiment which is particularly suitable for strip-shaped samples is configured such that the insert has a sample receiving chamber formed in its central part, a clamping gap extending from the sample receiving chamber radially outwardly relative to the transverse axis, and a rigid rod penetrating the sample receiving chamber in the direction of the transverse axis at a location radially spaced from the clamping gap, the rod with its ends being supported in recesses of the two lateral parts. In this case, the strip-shaped sample can be wound about the rigid rod and can be clamped with its free ends in the clamping gap. The sample is then tested with respect to tension.
An embodiment which is expedient for the pressure excitement of samples resides in that the insert has a sample receiving chamber formed in its central part, a support surface provided within the sample receiving chamber for radially supporting a sample relative to the transverse axis, and a counter abutment penetrating the sample receiving chamber in the direction of the transverse axis at a location radially spaced from the support surface and supported with its ends in recesses of the two lateral parts. In this case, a block-shaped or rod-shaped sample is clamped between the support surface and the counter abutment and the pressure forces introduced into the sample.
A measure which is particularly beneficial for manipulating the sample holder resides in that in the central part and the two lateral parts centering bores, aligned with one another in the direction of the transverse axis, are formed for receiving centering pins. By means of the centering pins the two lateral parts and the central part can be centered relative to one another and fixed, which facilitates the assembly of the sample holder when inserting different types of samples.
According to a further proposal of the invention, a contribution to the solution of the object is achieved, in particular, for a device of the aforementioned kind, in that the support is formed in the form of a tubular body surrounding the force transmission path with the transducer, the sample holder, the measuring device, and the adjusting device and having an access opening provided in the area of the sample holder.
The tubular body provided as a carrier enables a particularly bending-resistant configuration. This results in a beneficial oscillation behavior under the excitation force which is introduced into the force transmission path and whose reaction force is received by the carrier.
The preferred embodiment resides in that in the area of the sample holder two tempering chamber halves are provided which are slidable along a transverse axis extending transverse to the longitudinal axis between a closed position, in which they surround the sample holder, and an open position, in which the sample holder is exposed. In the open position the two tempering chamber halves can additionally be pivoted to the rear and top in order to provide an even better accessibility of the sample chamber. It is often desirable to perform the dynamic-mechanical analysis under different temperatures. The two tempering chamber halves produce in their closed position the desired temperature environment for the sample. On the other hand, in the open position the sample holder with the sample is easily accessible, in particular, for an exchange. Depending on the desired temperature, the two tempering chamber halves can be heated as well as cooled.
In this connection, a particularly expedient configuration is characterized in that the tempering chamber halves are arranged on two lateral arms supported on the tubular body.
Further features, details, and advantages result from the following description in which the invention is described in detail with the aid of one embodiment with reference to the drawing.